The art of spherical bearings and indeed bearings in general, requires the provision of precision engineered bearing surfaces wherein tolerances must be strictly adhered to ensure the smooth and effective operation of the bearings. As a consequence of keeping within these tolerances, bearings, and especially spherical bearings, are often expensive to manufacture.
Mounting the ball into the housing of a spherical bearing arrangement has proved difficult, since any method must result in the torque of the bearing being substantially zero. A conventional method is to provide a single ball and swage the housing around the ball to fixedly retain it therein. However, ensuring the torque of such a bearing remains within a predetermined range has proved difficult.
Spherical bearings comprising a split-ball arrangement go some way to alleviating the problems associated with single ball spherical bearings. Such an arrangement commonly comprises two split-ball portions which, when mounted together in the bearing housing, collectively define a split-ball arrangement which serves, in principle, as the ball of a single-ball spherical bearing arrangement.
The main advantage of split-ball bearings is that they do not require swaging of the bearing housing and thus reduce manufacturing costs. The split-ball portions are mounted in turn, with one portion being installed into the housing and engaging with the bearing surface, and the second portion being inserted and twisted by 90° to coincide with the other split ball portion. Consequently, it is easier to produce a split ball spherical bearing having a torque of substantially zero, since each part can be manufactured separately from one another.
Since spherical bearings are commonly used in the aerospace industry, weight is of paramount importance. It is desirable, therefore, to manufacture spherical bearings from a lightweight material, such as titanium or a titanium alloy. However, such a material does not offer the most desirable wear characteristics. In use, a shaft is commonly located in a bore passing through the ball of a spherical bearing. Over time, because the lightweight material of the bore does not offer a good wear surface, the bore bearing surface degrades, and the life of the bearing is shortened. The spherical bearing arrangement may therefore need to be scrapped at great financial cost.
In the case of a single-ball spherical bearing arrangement, a bushing can be interference fit in the bore to reduce wear on the ball. However, in the case of a split ball bearing arrangement, an interference fit bushing cannot be used without affecting the torque of the split ball bearing arrangement. Therefore, bushings are not used in split ball arrangements.
There is therefore a need for a split ball bearing arrangement manufactured from a lightweight material, but offering suitable wear characteristics for a shaft passing therethrough.